Control valves for hydraulic presses



June 24, 1958 J. M. TOWLER 2,339,897

CONTROL VALVES FOR HYDRAULIC PRESSES 1 Filed March 26, 1956 3 Sheets-Sheet 1 l/VVENTOE JOHN MAURICE TOWLERJECEASED BY FRANK HATHORN TowLER, EXE'GUTOR ORNEXS June 24, 1958 .1. M. TOWLER CONTROL VALVES FOR HYDRAULIC PRESSES 5. Sheets-Sheet 2 Filed March 26, 1956 fmmwmw M/TW JOHN JMAURICE Towl.

M VE/V ,6 ER 05cm 0 BY FRANK HATHORN TowLER Exa'cuToR June 24, 1958 J. M. TOWLER 2,839,897

' CONTROL VALVES FOR HYDRAULIC PRESSES I Filed March 26, 1956 3 Sheets-Sheet 3 |//V7'0/Z JOHN MAURICE TOWLER, oecsassv SY'FRAHK HATHORN TowLER, EXECUTOR 8) M, W ALMA/14% Arron/vars United States Patent CDNTROL VALVES FOR HYDRAULIC PRESSES Claims priority, application Great'Britain March 30, 1955 7Claims. (Cl. 60-52)..

This invention relates to control valves for hydraulic presses and particularly for direct-hydraulic presses of the type in which the pressure liquid for the operating stroke and return stroke of the hydraulic press is directly supplied by hydraulic pumps without the interposition of a hydraulic accumulator. Nevertheless it will be understood that a hydraulic accumulator may be used for auxiliary operations or to operate the control valves.

In particular this invention relates tocontrol valves for direct hydraulic forging and swaging presses in which it is desired to make a series of rapidly repeated short planishing strokes in addition to normal forging strokes.

The invention also relates to control valves for direct hydraulic presses for such operations as forging, coining, or forming, in which it is desired to secure almost instantaneous reversal :of the press ram upon completion of the pressing operation, or at a point controlled by the operator.

One object of this invention is to separate some of the primary pressure control valves from the pilot-pressure control valves, so that the primary-pressure valves may be mounted on or near their associated press cylinders thereby employing less large bore high pressure piping, and permitting most of the pilot-pressure valves to be mounted in a control panel conveniently located to suit the press operator.

A further object of this invention is to provide a directional control valve so constructed and arranged that the delivery of the primary pressure pumps does not pass through the said directional control valve to either the. press cylinder or return cylinders, and the said directional' control valve being soarranged that'the delivery of the primary pressure pumps is continuously connected to the return cylinders and the function of the new directional control valve is such as todirect pressure liquid to actuate admission valves to direct the delivery of the primary pressure pumps to the press cylinder for the forging stroke and alternately to actuate the prefill and exhaust valve for the return stroke. A Y Y A still further object of this invention is to provide a servo-actuated directional control valve of simple construction for the control of hydraulic forging presses and like'presses, the said control valve having only two operative positions, forwardfand return and for such valve to be servo-controlled by a simple reversingvalve.

Yet a further object of this invention is to arrange the servo-actuated directional control valve in a hydraulic system so that the primary pressure does not pass through the directional control valve to either the main cylinder or the return'cylinders but the said valve directs the primary pressure to actuate one or more admission valves to serve that purpose. For instance, all the primary pressure pumps may be in continuous communication with the return cylinders and one function of the said directional control valve is to direct primary or servo pressure to actuate an admission valve so as to admit primary'pressure from all the pumps tothe main cylinder to effect the, forging stroke and another function of the said directional control valveis to direct primary pressure or servo pressure to actuate the prefilling and exhaust valve 'of' the press in order to release liquid from the ,main cylinder of the press to effect the return stroke of the press ram as the said admission valve is closed.

it will be understood that, at the end of the forging stroke, reversal is effected by closing the admission valve and opening the prefilling and exhaust valve, and that the latter is effected by pressure in the'return cylinders, consequently it isessential that the action of these valves should be synchronised so as to effect rapid reversal. Thus it is a still further object of this invention to provide an admission valve so constructed and arranged in association with the said directional control valve that servo pressure and/or primary pressure are directed to the said admission valve so that it operates in the desired manner, some movements of the admission valve spindle being effected by primary pressure acting on one area of the spindle in opposition to servo pressure acting on another area of the spindle.

It is a furtherobject of this invention to provide a reversing valve so constructed that it may be actuated by an impulse of servo pressure supplied by a manuallyoperated or tappet-operated valve for reversing the press ram when a predetermined position is reached or actu ated by an impulse of primary pressure from the overblow of a relief valve in order to reverse the press ram at a predetermined pressure, the said reversing valve being provided with what might be termed a hydraulic detent in that it is held in the return position (to return the press ram) by servo pressure. It'will be understood that the said reversing valve may be designed to be actuated by an impulse of primary pressure it so desired without departing from this invention.

A further object of this invention is to provide improved means for regulating the length of the return stroke when making rapid planishing strokes on automatic cycle.

The. present invention consists broadly in a hydraulic system which comprises in combination with a hydraulic forging press having a main ram in a cylinder for effecting the forging stroke, one or more return rams and cylinders for effecting the return stroke of the main ram and a prefill and exhaust valve which is opened at the conclusion of the forging stroke to decompress the main cylinder and permit the main ram to make its return stroke, control means comprising two sets of primary pressure pumps which deliver directly to the one or more return rams and cylinders during the return stroke, a servo pressure liquid supply line having means for maintaining therein a supply of liquid at a predetermined pressure, an admission valve adapted to open automatically and pass the delivery of one set of pumps to themain press cylinder for a forging stroke of the press ram and to be closed by servo pressure to cause said set of pumps to deliver directly to the one or more return. cylinders, a servooperated reflux valve adapted to control the rate at which liquid is displaced from the one or more return cylinders during each forging stroke and to divert the same to the main press cylinder, servo pressure operated unloading valves for loading and unloading each set .of primary pressure pumps, a control valve which is manually operated to control the functions of the press and a'servo pressure operated distributing valve which operates under the control of the manually operable valve to distribute servopressure for eifecting operation of the servo pressure operated valves in the system and primary pressure for opening the prefill-' exhaust valve of the press. V

The invention also includes a hydraulic systemas above in which, in the control means a reversing valve is emvalve when the press is operating to planishing strokes.

acontrol valve in the said selected position.

In order that the invention may be clearly understood and 'put into practice an embodiment of the same will now be described, byway ofexample, by aid of the accompanying drawingsin which:

Fig. 1 is a diagrammatic arrangement of the system shown in conjunction with a downstroking forging press with the main control and distributing valves in the neutral position. i H

Figs; 2, 3 and 4 show the main control valve of Fig. l

in 'three further positionsof its valve spindle.

Figs. 5 and 6 show the distributing valve of Fig. l,

in two further positions of its valve spindle.

' The hydraulic systemillustrated in Fig. 1 isshown n conjunction with a downstroking forging press and in the figure A denotes the press cylinder and main ram,

B the returncylindcrs and rams for effecting the upward or return stroke of the main press ram, C the prefill exhaust valve to control the filling by gravity of oil from an. overhead tank Q, and, D a displacement piston and cylinder in which the displacement piston reciprocates .with the main press ram.

. The control gear of the present invention forming the hydraulic system illustrated in Fig. .1 comprises'a servopressure operated distributing valve E, a hand or lever operated main control valve U incorporating a reversing valve, a stroke control valve V, a normally open pilot pressure operated relay valve L, a normally closed pilot pressure operated relay valve S, a pump W for supplying servo-pressure, two sets of pumps Y and Z for supplying primary pressure for actuating the press, normally .open servo operated amplifier valves J and K which control the loading and unloading of the sets of pumps Y .and Z respectively, a reflux valve H which among other purposes hereafter to bedescribed functions to regulate the speed of the approach stroke of the press ram, and

a by-pass valve F.

In addition to the abovementioned main control valves the system illustrated also includes a fixed pressure master valve R functioning as a relief valve to limit the pressure of the liquid delivered by the two sets of primary pressure pumps Y, Z, a relief valve I to limit the pressure of the liquid delivered by the low pressure servo pump W, and

,a variable pressurerelief valve T to limit the pressure within the press cylinder A.

.Lever operated servo pressure control valve U This'v'alve, as shown in the drawings, has a valve spindle a operable by hand or other means through a lever b and to the left hand of the spindle a a further and separate spindle c which functions as a reversing make automatic The spindle a is formed in itslength with four reduced portions d, e, f and g separated by five full diameter portions as shown. The bore in the casing within which the spindle a works is formed with enlarged annular recesses and these communicate with the exterior of the casing by means of radial passages or connections indicated in the drawings by the numerals 1, 2, 3, 4, 5, 6,

7, 8, 9 but hereinafter referred to in the specification as U1,U2, U3, U4, U5, U6, U7, U8, U9. A passage 11 is provided within the casing which connects- US to U3 and a longitudinalpassage i is formed within the; interior of the valve spindle. This passage i communicates at each end with the interior of the bore by radial holes so as, to on occasions provide a connection between U2 and outlet U6 which leads to exhaust.

The separate spindle c is formed with a miter valve c1 adapted to coact with a seating within the bore containing the spindle c, and to the lefthand of this miter valve a reduced portion c2 opposite to the radial passage or connection U7. A small plunger j projecting from the left hand end of the spindle 0 extends into a space which receives primary pressure liquid through the radial passage or connection U8. The. right hand end of the spindle c is also provided with a small diameter PIOJCC- tion k which on occasion is adapted to be contacted by the opposing end of the spindle a and when so contacted to preserve an annular space which is open to exhaust by means of the connection U9. The head of the miter valve c1 is contained within an annular space which is connected to the connection U1 by means of a transfer passage 1 which although shown in the drawing as being on the exterior of the valve casing is in practice, formed within the thickness of the valve casing. A further interior transfer passage m is provided connecting connection U9 to the space at the extreme left hand end of the valve spindle c.

Servo pressure operated directional control valve E The directional control valve B is operated by servo pressure under the control of the lever operated valve U .and as illustrated in the drawings its valve member is for actuating the prefill valve C. The aforementioned openings or connections are indicated in the drawings by the numerals 1 to 12 and in this specification these are referred to as E1, E2, E3, E4, E5, E6, E7, E8, E9, E10, E11 and E12 respectively.

The shorter portion n of the valve member is separate from :the valve spindle 0 and its function is to act as a piston to force the spindle 0 to the right hand position in the drawing when the spindle of control valve U is moved by the operator into the hand reversal position shown in Fig. 5 of the drawings.

As in the case of valve U some of the connections in valve E are interconnected by internal transfer passages and in the valve illustrated these include a transfer passage p connecting E5 to a space p1 at the right hand end of the valve spindle 0, a transfer passage q containing a choke ql in its length and connecting E1 to E11,

.a transfer passage r having in its length a non-return or check valve r1 connecting E11 to E6, a transfer passage .9 connecting E6 to E6 and a transfer passage t connecting E7 to E7.

The spindle o is reciprocated to the right in the drawings by the admission of servo pressure through the connection 11 toan annular space between the two portions n and 0 of the valve member and to the left by the admission of servo pressure to the space p1 through the connection 5 and transfer passage 1 in which space it acts against the outer end of a small piston 01 forming an integral extension of the spindle 0.

Stroke control valve V v nections indicated on the drawings by the numerals 1, 1, each hereafter referred to as 'Vl. This through passage .also communicates with the cylinder 15 by a branch connection 17 containing a spring loaded check valve 18.

Freely reciprocable within the cylinder 15 and slidable over the spindle 10 is a piston 19. This piston is moved towards the right hand end of the cylinder 15 in the drawing by servo pressure delivered by the displacement ram D on the press through connection marked 2 on the drawings at the left hand end of the present valve V and the piston 19 is returned to the left hand end of its cylinder by servo pressure entering past the check valve 18 in the branch connection 17.

As the piston 19 moves to the right the liquid in advance of it within the cylinder passes out freely to the through passage V1 through the transfer passage 12'. When it closes the radial ports 13 the liquid becomes locked in the cylinder and the piston is halted. In a manner to be described this brings about actuation of valve E andreversal of the press ram. When the pressure at V2 falls, pressure is built up against the right hand side of the piston 19 and it is thereby returned to its normal position at the left hand end of its cylinder. It will thus be seen that the stroke of the press ram is determined by the position of the radial ports 13 in relation to the piston 19 and such relative position is varied by adjusting the position of the spindle 10.

Variable pressure relief valve T The relief valve T comprises a valve member 20 which is held closed by a spring whose tension is varied by a calibrated thimble nut'21. The force applied by the press ram -A is limited to a figure which is predetermined by adjustment of the nut 21. The left hand end of the valve member 20 is open to primary pressure through connection 1, hereafter referred to as T1 and when the predetermined pressure is exceeded the valve member 20 is forced to the right in the drawing until T1 connects with an outlet connection marked 5 and hereafter referred to as T 5. When this occurs primary pressure from T1 passes out through T5 to connection E11 of distributing valve E and acts to force the valve spindle of this valve to the right in the drawing to bring about reversal of the press ram A. The casing containing the spring of valve T is, permanently open to exhaust through connection marked 6.

The auxiliary apparatus shown in Fig. 1 includes:

(1) A relief valve R designed to limit the pressure of the liquid delivered by the primary pumps Y, Z,

(2) A delivery valve F for controlling the flow of primary pressure fluid from pumps Z to. the main press cylinder A, relief valve T and connection US of control valve U,

(3) Servo operated valves J and K designed to load and; unload the primary pressure pumps Y and Z respectively,

(4) A normally open valve L which is closed by servo pressure under control of main valve U to shut off servo pressure from the valves J and K,

(5) A normally closed reflux valve H which'is opened against spring pressure by primary pressure and servo pressure alternatively,

(6) A, spring loaded'accumulator I to maintain a volume of servo pressure liquid in the servo pressure system and designed also to act as a relief valve to limit the pressure in said servo pressure system,

(7) A normally closed servo operated relay valve S.

In Fig. l the larger diameter pipes carry primary pressure liquidand the smaller'diameter pipes servo pressure liquid. 7

Referring to Fig. 1 the press cylinder is filled from the overhead tank Q- through the prefill valve C, that is to say that the press cylinder draws liquid from tank Q through the prefill valve on the gravity downward stroke of the press ram and on the return stroke it returns pressure liquid. through the decompression valve into tank Q to decompress the press cylinder and, when the prefill valve is held open, liquid is returned to the tank Q on the upward or; return stroke of the press ram A. The servopressure actuated directional control valve E serves to actuate auxiliary valves in order to direct pressure liquid from the primary pressure mps Y, Z to the main cylinder A and the return cylinders B so as to control the movement of the press ram and to unload the primary pressure pumps when the press ram is inoperative, and it also actuates the prefill and exhaust valve C in order to effect the decompression of the press, cylinder and hold the prefill valve open during the rapid return stroke of the press ram. Servo-pressure is supplied by the servopump W primary pressure. liquid to operate the press rams is provided by the five pumps Y and Z. The primary pressure pumps are continuously connected to the return cylinders B and primary pressure liquid from the pumps may be admitted to the main cylinder through the admission valve F which is opened by primary pressure against its spring and reflux valve H which is opened against its spring by primary pressure or by servo-pressure during automatic planishing. When the pumps are unloaded the press ram A is prevented from falling by the liquid being locked in the return cylinders B by means of check valves X2 and X11 and the reflux valve H which is closed on the return stroke. The function of valve H is to regulate the speed of the approach stroke. On the forging stroke, valve H acts as a relief valve between the return cylinders and the main cylinder and on automatic planishing strokes the valve H regulates the speed of the approach stroke; itis opened on the down stroke by servo-pressure when doing automatic planishing strokes, but on forging strokes it is opened by primary pressure and closed on the up stroke by spring and servo-pressure. The unloading valve 1 is intended to load and unload the two primary pressure pumps Y. The unloading valve K is intended to unloadthe three primary pressure pumps Z. The valve L is actuated by a tappet valve N to limit the return stroke 'ofthe press ram A. A further tappet valve 0 limits the down stroke by actuating unloading valve J and also unloading valve K. These valves '3 and K maybe constructed in accordance with out co-pending U. S. application Serial No. 324,104 filed December 4, '1952, now Patent No. 2,805,038. The relief valve Ris designed to limit the pressure of the liquid delivered by the primary pressure pumps and this relief valve may be constructed in accordance with our co-pending U. .8. application Serial No. 430,339 filed May 17, 1954, but any other suitable formof relief valve may be used. The construction of valve L is substantially as shown in sectionin Fig. 1. The valve S is of slightly'different construction and is as shown in section'in Fig. l. The valve S is designed to direct servo-pressure from connection E4 of the directional control valve E to connection 3 of valve H during automatic'planishing strokes. The control valve U is operated by means of a hand lever not shown to direct servo-pressure to the directional control valve E to cause the press ram 'Ato make a downward stroke and as pressure is built up in the cylinder A as the ram contacts the forging, the same pressure is applied to the small spindle j at the extreme left of valve U in the drawing which acts in opposition to the force applied to the hand-lever so that the force applied by press'ram A is substantially proportional to the force applied to the hand-lever and, if this is exceeded, spindle U is moved to reverse the press, ram. Alternatively the press may be reversed by the relief valve T acting through the valve E as will be described later. During-rapid. planishing strokes, the length of the return stroke is regulated by valve V as previously described.

The spindle 22 of the admission valve F has area 23 and a seat area 24 and it is forced into the closed position by a spring. When the spindle 22 is up, thereby coupling its connection P1 with its connection F2, pressure at F1 acts on area 23 audit is opposed by pressure at a connection F3 plus the force of the spring. On the other hand, when the spindle is down, thereby a piston action only.

isolating connection F1 from F2, pressure at c'onnection F1 acts on the annular area 23 plus pressure at F2 acting on the area 24 under the seat and opposed by the pressure at P3 acting on the area above the piston plus the force of the spring.

Neutral When the hand operated four. position control valve U is in the neutral position shown in Fig. 1 servo-pressure from the servo pump W passes through connections 1 of the stroke control valve V and to connection US of valve U. It is then directed by the internal drilling h and neck or reduced portion 1 in the spindle to connection U4 which is coupled to connection E5 on the pressure actuated directional control valve E, and pressure is directed to act on the small plunger 01 at the righthand end of valve E by the internal drilling p: the spindle of valve E is thus held in the left-hand or forge position shown in Fig. 1. It is. to be noted that connection E of valve E is also in communication with the stroke control cylinder D on the press. Connection E5 is also coupled to connection E8 by a reduced portion or neck on the spindle o.

Alsowith the valve U in this neutral position connection U3is joined to U6 by reduced portions d, e in the spindle a and because connection U6 is piped to exhaust the line at connection U3 is also to exhaust. This line is joined to connection 6 of E where it takes two paths, one straight through the internal drilling s in E to connection 1 of the fixed pressure relay valve L, the second via a neck in the spindle 0 to connection E4 on E and thus to connection 2 of S.

With U in the neutral position there is no supply of servo-pressure to connection 1 of L and 2 of S and therefore, no servo-pressure to connections 3 of valves I and K which are therefore open, their spindles being raised to unload all primary pressure pumps.

Also with valve U in this neutral position its connection U1 is to exhaust at.connection U6 along the reduced portion d in its spindle a, and as connection U1 is also in communication with connection 4 of the fixed pressure servo valve S, the lack of servo pressure in this line allows this valve S to come to the closed position.

As connection 1 of S is open to exhaust through its connection 3 therefore connection 3 of the normally closed amplifier H is also connected to exhaust allowing it to close,'and isolating its connections 1 and 2. Hence the press is held up as connection 1 of H is piped to the return cylinders B and pressure is also locked by the check valves X2 and X11. 7

Connection E10 of valve E is open to exhaust along a reduced portion of its valve spindle o to connection E7, the prefill valve C connection 1 is therefore open to exhaust and C is closed by associated springs.

Connection 30f F, the pressure actuated seated bypass-valve, is open to exhaust through connections E1 and E7 of valve E, thus F remains closed due to spring Forge ;When. thecontrol lever moves the spindle of valve U to the forge position shown in Fig. 2 connection U1 remains coupled to exhaust atconnection U6, thus valve S remains closed, as there is no pressure on its connection 4. .Also connection U2 of valve U is coupled to U6 and exhaust by its axial passage i, thus there is no pressure on connection E12 of valveE. Also a servo-pressure line, by-passing valve B through check valve X6 puts pressure on connection E5 of E and on the small end 01 of the valve spindle 0, thus the spindle 0 of valve E is retained in its left-hand or forge position Fig. 1. Con- 8 nection E5 on valve E is also inconnection with E8, via the neck in its spindle, and from E8 it is piped hack into the servo supply line. Connection US on valve U is open to connection U3 via the internal drilling h and neck f in the spindle a. Therefore, servo-pressure passes through the internal passage s in the valve E to connection 1 on L, which is in its normally open position, thus, servo-pressure goes to connections 3 on the valves J and K and this will push the spindles down on to their seats so shutting off their connections 1 from exhaust via connections 2. Thus, all primary pressure pumps are loaded. Due to servo-pressure passing through a choke in check valve X10, K will function slightly after J, thus loading the two sets of pumps Y and Z in sequence.

As there is no servo-pressure in the line connection E1 on valve E to connection 3 on F, primary pressure acting on connection 10f F will lift the spindle of F thus joining connection 1 to 2 and hence the pumps Z can deliver to the main cylinder.

The pumps Y deliver via check valves X12 and X11 to connection 1 of valve H. As spring load only is holding valve H closed the valve opens at the pressure required to overcome the spring and the pumps deliver through connection 2 into the main cylinder line. The

press moves down at a speed given by the pump output,

oil displaced from the return cylinders B passing through connections 1 and 2 of H into the main cylinder line.

The main cylinder pressure line is also in communication with connection 1 on T and connection U8 of valve U.

7 Build up to pressure exceeding setting of valve T When the pressure has built up in the main cylinder above the setting of the variable pressure relief valve T, which has main cylinder pressure on its connection 1, it will relieve via connection 5 on T to connection E11 on valve E so moving the spindle 0 of valve E to the right.

Movement of the spindle 0 in E to the right brings the valve to the automatic return position, Fig. 5 and connecting connection E6 to E1 through the internal drilling q and choke q to E11. Thus, as connection E6 is subject to servo-pressure as previously described, the same servo-pressure acts through connection E1.to E11 on the left-hand area of spindle 0 as the spindle area is greater than that of the small plunger 0 at the extreme right of valve E. The spindle 0 of valve E is thus maintained in the automatic return position. In this position connection E9 is coupled to E10 and therefore the primary pumps Y are coupled to the operating piston 27 of the prefill and exhaust valve C thus opening the decompression valve 26.

At the same time servo-pressure from connection E6 via connection E1 and connection 4 of valve H closes down the valve of H and the pumps Y are cut from the main cylinder A and deliver only to the return cylinders B. When the main cylinder A has been decompressed to approximately 500 p. s. i. the large prefill and exhaust valve 25 opens, valve F closes by servo-pressure from E6 via E1 applied at connection 3 of valve F and all pumps now deliver to the return cylinders B and the press ram returns.

The extent of a return stroke is controlled by either of the following methods:

(1) Returning valve U to neutral position, or

(2) Contacting top stop N.

By returning the valve U to neutral position during the return stroke, servo-pressure is cut oil? from connection U3 by U3 being joined to U6 and exhaust, which opens connection 3 of valve J and connection 3 of valve K to exhaust via L2 and L1 to U3 and allows the amplifiers J and K to open and unload the pumps. Because servo-pressure is cut off from E6 it will be cut off from E1 and E11, but as US is through to U4 servo-pressure is on E5 which causes the spindle of valve E to return .9 to the press position. Pressure liquid is locked in cylinders B by valve H as described previously under Neutral.

When the tappet valve N is contacted at the limit of the upward stroke of the press ram connections 1 and 2 on N are joined, thus directing servo-pressure on to connection 4 of L causing its spindle to lift, isolating its connection 1 from connection 2 and connecting 2 to exhaust port 3. This allows the amplifiers J and K to open and unload the pumps as previously described. The press ram is held up by pressure locked in the return cylinders by H and check valves X2 and X11.

Automatic planishing strokes In order to make automatic planishing strokes, valve U is placed in the automatic position Fig. 3, and the lever actuated spindle is held in contact with the reversing valve at the left-hand end. In this position connection U5 is open to U1 and U3 and these connections are isolated from exhaust at connection U6 by the spindle a. Therefore, servo-pressure is applied to connection 4 on valve S lifting the spindle and opening its connection 2 to 1. Servo-pressure is now applied through connections E4 and E6 on valve E to 2 on valve S, the spindle being open to 1, pressure can pass to connection 3 of H thereby lifting the spindle of valve H and opening its connections 1 to 2 and giving free passage of oil from the return cylinders B to the main cylinder A.

The press ram A can now fall freely by gravity, the speed of fall being controlled by the setting of valve H. Because the main ram is falling faster than pumping speed, the prefill and exhaust valve C will open allowing oil to flow by gravity into the main cylinder. The primary pressure pumps are loaded as previously described. On contacting the work the prefill and exhaust valve C is closed and pressure builds up in the main cylinder, this pressure is also applied to the small spindle j at the left-hand end of U. The load thus applied by the small spindle to the reversing valve 0 is opposed by the load applied at the hand lever of valve U. When the load applied by the small plunger is greater than the load applied by the hand lever, the spindle and reversing valves are moved slightly to the right. This motion opens connection U1 to U7 through the reversing valve seat on valve U and servo-pressure is applied through connection E11 on valve E to the left-hand end of the spindle c in valve E. The spindle of E is thereby moved to the automatic reversal position Fig. 5 and reversal takes place as described under Forge. It should be noted that the load applied by the press is substantially proportional to the load applied to the hand lever on valve U.

On the return stroke, oil is displaced from the control cylinder D to connection 2 on valve V causing the piston 19 in. valve V to move to the right and oil displaced by the piston passes through the ports in the spindle into the servo-pressure line. When the movement of the piston [covers the left-hand ports 13 in the spindle, pressure builds up in the line connection 2 to the stroke control cylinder D which is in communication with connection E5 on valve E and through the internal drilling p in valve E to the small plunger 01 at the right-hand end. When the force on this plunger 01 exceeds the force applied "by servo-pressure at the opposite end of the spindle, valve E spindle 0 is moved back to the forge position Fig. l and the automatic planishing stroke is repeated. The length of return stroke is determined by the setting of stroke control valve V as previously described. The press will operate automatically as long as valve U is held in the Auto position. It will be seen that the difference between forge and automatic is that in the forge position the press ram makes a single stroke and is pumped down at pump speed, whereas in the Auto position the press ram falls by gravity and makes repeated strokes.

Hand reversal by operator In order to make a hand reversal the position of valve U is moved to the hand reversal position, Fig. 4.

In this position connection U1 on valve U is open to connection U6 and exhaust, also connection U5 is open to U2, U3 and U4. Servo-pressure is now applied through connection U2 to connection E12 on valve E thereby pushing the spindle of E to the right into the return position Fig. 6. The press is now returned as previously described. With U in the hand return position Fig. 4, valve V is inoperative as U4 is coupled to US, and therefore cylinder D cannot create a pressure in excess of servo-pressure, thus the press will rise until the single interrupter valve N is contacted, when the press ram is stopped and is held by pressure liquid locked in the return cylinders 'by valve H as previously described.

Overstroke Should the single interrupter 0 be contacted due to overstroke' of the press ram, servo pressure at connection 1 will pass to conection 2 and thus to connection 4 on L, lifting the spindle and shutting off connection from 2. This interrupts servo-pressure going to connection 3 on J and K allowing their spindles to lift and unload the primary pressure pumps.

To return the press ram, the handle of valve U is moved to the return position, thus connection US will be coupled to U2 and servo-pressure will be directed to connection l2 on E pushing the spindle to the right, this shuts off connection 4 of E from servo-pressure of connection 6 of E thus servo-pressure is removed from connection 1 on O and hence connection 4 on L, this allows the spindle in L to return to its normally open position, which allows servo pressure to pass from connection 6 on E via connections 1 and 2 on L to connections 3 on J and K, thus closing down their spindles and loading the 1. In combination with a hydraulic forging press hav-. 7

ing a main ram in a cylinder for effecting the forging stroke, one or more return rams and cylinders for effecting the'return stroke of the main ram and a prefill and exhaust valve which is opened at the conclusion of the forging stroke to decompress the main cylinder and permit the main rain to make its return stroke, control means comprising two sets of primary pressure pumps connected by conduit means to deliver directly to the one or more of the return ram cylinders during the return stroke, a servo pressure liquid supply line having means for maintaining therein in a supply of liquid at a predetermined pressure, an admission'valve connected to said conduit means and opened by the pressure therein to pass the delivery of one set of pumps to the main press cylinder for a forging stroke of the press ram, said admission valve being closed by servo pressure and operative when closed to cause said set of pumps to deliver directly to the one or more return cylinders, a servo operated reflux valve connected in said conduit means to control the rate at which liquid is displaced from the one or more return cylinders during each forging stroke and to divert the same to the main press cylinder, servo pressure operated unloading valves for loading and unloading each set of primary pressure pumps, a manually operable control valve, a servo pressure operated distributing valve controlled by the manually operable valve trol valve so that the press ram is caused to performa series of rapidly repeated planishing strokes the force of whichis substantially proportional to the load applied by the operator in holding the manualcontrol valve in the said selected position against a force exerted by the reversing valve. 7

3. Control means according to claim 2 wherein the reversing valve consists in a miter valve on a piston which is co-axial with the spindle of the manual control valve,

said miter valve being held on. its seat by the spindle of.

' ations are continuously repeated whilst the operator holds the manual valve spindle in the one selected position.

,4. Control means according to claim 2 which includes a stroke control valve which comprises a manually adjustable spindle and a piston which is movable over the spindle by pressure liquid displaced during the return stroke of the press ram by a ram which reciprocates with the press ram in a cylinder, said piston displacing liquid in advance of itself through an outlet port in the manually adjustable spindle until said outlet port is covered by the piston and the movement of the piston is halted when the pressure in the cylinder containing the said ram builds up and effectsdisplacement of the spindle of the servo operated distributing valve to its forge position and the repeating of the automatic planishing stroke.

5. Control means according to claim 2 wherein the manual control valve has four operative'positions into which its valve member may be moved and in each of whichIthe'press is caused to perform a different function, as follows: neutral in which all pumps are unloaded, forge in which the press ram performs a normal forging stroke, auto in which the press ram makes a series of rapidly repeated short planishing strokes and return in which the press ram is reversed under the control of the operator.

6. Control means as in claim 5 wherein the valve member of the directional control valve is reciprocated between two operating positions by servo pressure under control of the manual control valve, in one operating position to cause the press ram to make a forge stroke and in the other operating position to cause the press ram to make its return stroke.

7. Control means according to claim 1 which includes two servo pressure operated relay valves one of which is arranged to control an operation of the reflux valve and the other to control the opening and closing of the two pump unloading valves.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nos 2 839;,897

John Maurice Towler, deceased,

by Frank Hathorn Towler, executor,

June 24 1958 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6 line 40 for "out co==pending U, 5., application" read as our co pending vUr, S, application column 10, line 50, after "therein" strike out "in" c (SEAL) Attest:

KARL Ho AXLINE Attesting Oificer ROBERT C. WATSON Commissioner of Patents 

